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2023.1.30
Vickers hardness tester is applicable to the hardness measurement of larger workpieces and deeper surface layers. Here let’s go through an overview of the Vickers hardness tester, including principles, classification, application, advantages, and disadvantages.
The quotient of the test force divided by the surface area of the indentation is the Vickers hardness number. Vickers hardness value calculation formula: HV=constant × Test force/indentation surface area, where HV is the Vickers hardness symbol, F is the test force (in N), and d is the arithmetic mean of the two diagonal lines d1 and d2 of the indentation (in mm). Vickers hardness value can be obtained by looking up the table according to the diagonal length d. The national standard stipulates that the Vickers hardness indentation diagonal length range is 0.020~1.400 mm. See the diagram of Vickers hardness tester test principle below.
The Vickers hardness tester is expressed as HV, and the value in front of the Vickers hardness symbol HV is the hardness value, followed by the test force value. The standard test holding time is 10~15S. However, for non-ferrous metals, it should not be less than 30 seconds. If the selected time is outside this range, the holding time should be noted after the force value. For example, 300HV30 indicates that the hardness value obtained when the test force is 294.2N (30kg) and the holding time is 10~15S is 300.
The Vickers hardness tester is divided into three types according to the different test forces: Vickers hardness tester, low load Vickers hardness tester, and micro Vickers hardness tester. The test force shall be selected according to the sample type, sample thickness, and expected hardness range. The standard stipulates that the thickness of the sample or test layer shall be at least 1.5 times the diagonal length of the indentation.
Vickers hardness tester is mainly used for material research and scientific tests. The small-load Vickers hardness test is mainly used to test the hardness of small precision parts, the hardness and depth of the hardened layer, the surface hardness of the coating, the hardness of the thin sheet material and thin wire material, the hardness near the blade, the hardness of the dental material, etc. Because the test force is very small, the indentation is also very small, and the appearance and use performance of the sample can not be affected. Micro Vickers hardness test is mainly used for metallographic and metallographic research. It is used to measure the hardness of each constituent phase in the metal structure and to study the brittleness of refractory compounds. Micro Vickers hardness test is also used to test small or thin parts. The thickness of parts can be as thin as 3 μ m.
1) Advantage:
– Vickers hardness tester is used for measuring the thinner Vickers hardness value. Use a diamond indenter with a square pyramid to press into the surface of the sample under the action of the test force. After holding the test force for a specified time, remove the test force and measure the diagonal length of the indentation on the surface of the sample. The indentation of the Vickers hardness tester is square, with a clear outline and accurate diagonal measurement. Therefore, the Vickers hardness test is one of the commonly used hardness test methods, and its repeatability is also very good, which is better than the Brinell hardness tester.
– The Vickers hardness tester has a wide range of measurements, which can measure metal materials used in industry at present, from very soft materials (several Vickers hardness units) to very hard materials (3000 Vickers hardness units).
– Vickers hardness tester test is that its hardness value is independent of the size of the test force. As long as it is a material with uniform hardness, the test force can be selected, and its hardness value remains unchanged. This is equivalent to having a unified scale in a wide range of hardness. This is better than the Rockwell hardness test.
– In the range of medium and low hardness values, on the same uniform material, Vickers hardness test and Brinell hardness test results will obtain approximate hardness values. The test force of the Vickers hardness tester can be as low as 10gF, and the indentation is small, which is suitable for testing thin and small materials.
2) Disadvantages:
– Vickers hardness tester has low test efficiency, requires high test, and requires a high surface finish of the sample. Generally, the sample that needs to be made is troublesome and time-consuming and is usually only used in the laboratory.
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